Some grids have fluidizing air injection openings which may become blocked by solid particles falling into them.
This applies in particular to grids in which the openings flare upwards, being in the form of truncated cones or of truncated pyramids, for example. Each time fluidization is stopped, these openings are obstructed by solid particles falling back onto the grid. Therefore, in order to fluidize the particles again, it is necessary to clear the openings by an operation referred to as "unclogging". The openings through the grid become obstructed because the pipe feeding injection gas to the grid includes either a bend or else a siphon in order to prevent the particles from penetrating into all of the injection pipework when fluidization is stopped.
Various devices have been used up to the present for unclogging. One such device consists in feeding each opening in the grid individually by means of a duct which includes a flow rate adjusting valve, a stop valve, a diaphragm, and siphon means for retaining poarticles. When accumulation occurs therein, the stop valve is closed and the accumulated particles are blown out by compressed air. These means are effective, but complicated and expensive.
Another known solution to this problem consists in placing an element in the injection pipe for retaining particles in one direction while allowing air to pass in the opposite direction. This element is simple but it introduces major headloss in the fluidization installation.
Finally, there exists a solution whereby unclogging is achieved by applying compressed air to the clogging mass via a small diameter pipe situated in the fluidizing orifice. This solution is effective, but it requires two feed networks for the fluidizing orifices and that constitutes a factor which increases cost.
The present invention seeks to provide a different solution to this problem of particles clogging the orifices in a fluidizing grid, which solution avoids the complexity of prior devices by making it possible to use the fluidizing gas for unclogging purposes.